[Bug libgcc/85334] Shadow stack isn't unwound properly through signal handler

[hjl at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85334

--- Comment #3 from hjl at gcc dot gnu.org <hjl at gcc dot gnu.org> ---
Author: hjl
Date: Thu Apr 19 17:05:39 2018
New Revision: 259502

URL: https://gcc.gnu.org/viewcvs?rev=259502&root=gcc&view=rev
Log:
libgcc/CET: Skip signal frames when unwinding shadow stack

When -fcf-protection -mcet is used, I got

FAIL: g++.dg/eh/sighandle.C

(gdb) bt
 #0  _Unwind_RaiseException (exc=exc@entry=0x416ed0)
    at /export/gnu/import/git/sources/gcc/libgcc/unwind.inc:140
 #1  0x00007ffff7d9936b in __cxxabiv1::__cxa_throw (obj=<optimized out>,
    tinfo=0x403dd0 <typeinfo for int@@CXXABI_1.3>, dest=0x0)
    at /export/gnu/import/git/sources/gcc/libstdc++-v3/libsupc++/eh_throw.cc:90
 #2  0x0000000000401255 in sighandler (signo=11, si=0x7fffffffd6f8,
    uc=0x7fffffffd5c0)
    at /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:9
 #3  <signal handler called> <<<< Signal frame which isn't on shadow stack
 #4  dosegv ()
    at
/export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:14
 #5  0x00000000004012e3 in main ()
    at
/export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:30
(gdb) p frames
$6 = 5
(gdb)

frame count should be 4, not 5.  This patch skips signal frames when
unwinding shadow stack.

gcc/testsuite/

        PR libgcc/85334
        * g++.dg/torture/pr85334.C: New test.

libgcc/

        PR libgcc/85334
        * unwind-generic.h (_Unwind_Frames_Increment): New.
        * config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment):
        Likewise.
        * unwind.inc (_Unwind_RaiseException_Phase2): Increment frame
        count with _Unwind_Frames_Increment.
        (_Unwind_ForcedUnwind_Phase2): Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/torture/pr85334.C
Modified:
    trunk/gcc/testsuite/ChangeLog
    trunk/libgcc/ChangeLog
    trunk/libgcc/config/i386/shadow-stack-unwind.h
    trunk/libgcc/unwind-generic.h
    trunk/libgcc/unwind.inc